Field of the Invention
The present invention relates to a pressure switch including a pressure sensor, which outputs an output signal based on a pressure value detected by the pressure sensor.
Description of the Related Art
Heretofore, for example, by supplying a negative pressure fluid with respect to a suction transport means such as a suction pad or the like, transporting of a workpiece to a predetermined position is carried out while the workpiece is attracted under suction by the suction pad. In this case, a pressure switch is used for confirming whether or not the workpiece has reliably been attracted, by the pressure value of the negative pressure fluid that is supplied to the suction pad reaching a predetermined pressure. With such a pressure switch, in general, a semiconductor pressure sensor is used that functions as a pressure sensor, and based on a resistance value, which is changed by a pressure applied to the pressure sensor, a pressure of a fluid is detected, and it is judged whether a workpiece is attracted, and a detection signal is output therefor when the pressure value detected by the pressure sensor matches with a preset pressure value that has been set beforehand.
To such a pressure switch, for example, a vacuum pipe is connected detachably through a tube joint to a pressure inlet port of a housing in which the pressure sensor is housed, and a negative pressure fluid that flows through the vacuum pipe is introduced into the housing, whereby the pressure of the negative pressure fluid is detected (for example, refer to Japanese Laid-Open Patent Publication No. 07-037473). Further, though not disclosed in Japanese Laid-Open Patent Publication No. 07-037473, generally, as a seal structure for maintaining airtightness between the pressure sensor and the housing, a structure is adopted in which an O-ring is arranged between the pressure sensor and the housing.